I would lay odds that if it is bath 3 there may be sulfation from old saturated blix building up in the llnes. Filp the thing (I wound my replenishment hoses up inside since I don't use them, and they are always in the way when flopped out.

ABS cement and shavings from a cut off black plumbing pipe may be a good fillier for your leak. Otherwise black RTV gasket maker for automotive uses can work well in these kind of situations.

The pumps are magnetic drive. If they don't spin well, the magnetic current just heats the stator of the motor. The motors are thermally protected to save against a melt down , and run off of 100V - that is what the transformer does - steps motor and controls down from 120v. The heaters are 120 powered though. I spent quite a while 'under the hood' of mine to figure some of this stuff out.

Remove the clips, and take the hoses off the tank and pump on tank 3. I think you will find a sulfur build up, or maybe even silver flakes if the blix was saturated. Something likel that , or a great deal of somethings like clumps of iron may also be attrached to the motor and 'magnetically shorting it out', or have plated onto the shaft.

I never could get my digital tank 1 thermostat to work. I replaced it with an analaog thermostat, and now run mine as tank 1 pre wet, tank 2 deve, tank 3 b/f and it works well this way. I have spare analog thermostats if it comes to that for you. I bought 5, when I needed one, because the price was right.

Watch out for dead tensioning springs on the racks. I replace mine with rubber drive belts of the sort you would replace in a cassette deck/8 track from an electronics wholesaler.